* Brian Gerst <brge...@gmail.com> wrote:
> > Something like this:
> >
> > taskset 1 perf stat -a -e '{instructions,cycles}' --repeat 10 perf bench
> > sched pipe
> >
> > ... will give a very good idea about the general impact of these changes on
> > context switch overhead.
>
> Before:
> Performance counter stats for 'system wide' (10 runs):
>
> 12,010,932,128 instructions # 1.03 insn per
> cycle ( +- 0.31% )
> 11,691,797,513 cycles
> ( +- 0.76% )
>
> 3.487329979 seconds time elapsed
> ( +- 0.78% )
>
> After:
> Performance counter stats for 'system wide' (10 runs):
>
> 12,097,706,506 instructions # 1.04 insn per
> cycle ( +- 0.14% )
> 11,612,167,742 cycles
> ( +- 0.81% )
>
> 3.451278789 seconds time elapsed
> ( +- 0.82% )
>
> The numbers with or without this patch series are roughly the same.
> There is noticeable variation in the numbers each time I run it, so
> I'm not sure how good of a benchmark this is.
Weird, I get an order of magnitude lower noise:
triton:~/tip> taskset 1 perf stat -a -e '{instructions,cycles}' --repeat 10
perf bench sched pipe >/dev/null
Performance counter stats for 'system wide' (10 runs):
11,503,026,062 instructions # 1.23 insn per cycle
( +- 2.64% )
9,377,410,613 cycles
( +- 2.05% )
1.669425407 seconds time elapsed
( +- 0.12% )
But note that I also had '--sync' for perf stat and did a >/dev/null at the end
to
make sure no terminal output and subsequent Xorg activities interfere. Also,
full
screen terminal.
Maybe try 'taskset 4' as well to put the workload on another CPU, if the first
CPU
is busier than the others?
(Any Hyperthreading on your test system?)
Thanks,
Ingo
